Cloud environment setup

Environments define the sandbox configuration where your agent runs. You create an environment once, then reference its ID each time you start a session. Multiple sessions can share the same environment, but each session gets its own isolated sandbox (a fresh Linux container).

This page covers type: cloud environments. To run sandboxes on your own infrastructure, see Self-hosted sandboxes.

Create an environment

ant apply environment.yaml

name: python-dev
config:
  type: cloud
  networking:
    type: unrestricted

Use a unique, descriptive name so you can tell environments apart.

Use the environment in a session

Pass the environment ID as a string when creating a session.

ant beta:sessions create --agent "$AGENT_ID" --environment-id "$ENVIRONMENT_ID"

Configuration options

Packages

The packages field pre-installs packages into the sandbox before the agent starts. Packages are installed by their respective package managers and cached across sessions that share the same environment. When multiple package managers are specified, they run in alphabetical order (apt, cargo, gem, go, npm, pip). You can optionally pin specific versions. Unpinned packages install the latest version. If the environment uses limited networking, also set networking.allow_package_managers to true; otherwise the request is rejected with a 400 error.

ant apply environment.yaml

name: data-analysis
config:
  type: cloud
  packages:
    pip:
      - pandas
      - numpy
      - scikit-learn
    npm:
      - express
  networking:
    type: unrestricted

Supported package managers:

Networking

The networking field controls the sandbox's outbound network access. It does not affect the web_search or web_fetch tools, which run on Anthropic's servers; to restrict the sites those tools can reach, set allowed_domains or blocked_domains on the tool's entry in the agent toolset. See Restrict web search and web fetch domains.

The following example creates an environment with limited networking:

ant apply environment.yaml

name: api-access
config:
  type: cloud
  networking:
    type: limited
    allowed_hosts:
      - api.example.com
    allow_mcp_servers: true
    allow_package_managers: true

When using limited networking:

• allowed_hosts specifies domains the sandbox can reach. Specify bare hostnames or wildcard patterns (such as *.example.com). Do not include a URL scheme, port, or path.
• allow_mcp_servers allows outbound access to MCP server endpoints configured on the agent, beyond those listed in the allowed_hosts array. Defaults to false.
• allow_package_managers allows outbound access to public package registries (such as PyPI and npm) beyond those listed in the allowed_hosts array. Defaults to false. Set it to true whenever the environment specifies packages; otherwise the request is rejected with a 400 error, even if the registry hosts are listed in allowed_hosts.

Environment lifecycle

• Environments persist until explicitly archived or deleted.
• Each session gets its own sandbox instance, even when multiple sessions reference the same environment. Sessions do not share filesystem state.
• Environments are not versioned. If you update an environment frequently, keep your own record of the changes so you can tell which configuration each session used.

Manage environments

# List environments
ant beta:environments list

# Retrieve a specific environment
ant beta:environments retrieve --environment-id "$ENVIRONMENT_ID"

# Archive an environment (read-only, existing sessions continue)
ant beta:environments archive --environment-id "$ENVIRONMENT_ID"

# Delete an environment (only if no sessions reference it)
ant beta:environments delete --environment-id "$ENVIRONMENT_ID"

Pre-installed runtimes

Cloud sandboxes include common language runtimes, databases, and command-line tools out of the box. See Cloud sandbox reference for the full list.

Next steps